The present invention is related to a composite box structure and more particularly to a composite box structure assembled on and attached to a railway car underframe to provide an insulated railway boxcar or a temperature controlled railway car.
Over the years, general purpose railway boxcars have progressed from relatively simple wooden structures mounted on flat cars to more elaborate arrangements including insulated walls and refrigeration equipment. Various types of insulated boxcars are presently manufactured and used. A typical insulated boxcar includes an enclosed structure mounted on a railway car underframe. The enclosed structure generally includes a floor assembly, a pair of side walls, a pair of end walls and a roof. The side walls, end walls and roof often have an outer shell, one or more layers of insulation and interior paneling.
The outer shell of many railway boxcars often has an exterior surface formed from various types of metal such as steel or aluminum. The interior paneling is often formed from wood and/or metal as desired for the specific application. For some applications the interior paneling has been formed from fiber reinforced plastic (FRP). Various types of sliding doors including plug type doors are generally provided on each side of conventional boxcars for loading and unloading freight. Conventional boxcars may be assembled from various pieces of wood, steel and/or sheets of composite materials such as fiberglass reinforced plastic. Significant amounts of raw material, labor and time are often required to complete the manufacture and assembly of conventional boxcars.
The underframe for many boxcars include a center sill with a pair of end sill assemblies and a pair of side sill assemblies arranged in a generally rectangular configuration corresponding approximately with dimensions for the floor of the boxcar. Cross bearer 217 are provided to establish desired rigidity and strength for transmission of vertical loads to the associated side sills which in turn transmit the vertical loads to the associated body bolsters and for distributing horizontal end loads on the center sill to other portions of the underframe. Cross bearer 217 and cross tie 216 cooperate with each other to support a plurality of longitudinal stringers. The longitudinal stringers are often provided on each side of the center sill to support the floor of a boxcar. Examples of such railway car underframes are shown in U.S. Pat. Nos. 2,783,718 and 3,266,441.
Some railway cars or boxcars may be manufactured using side wall assemblies with all or portions of a respective side sill assembly formed as an integral component thereof. In a similar manner, such railway cars and/or boxcars may also be manufactured with end wall assemblies having all or portions of a respective end sill formed as an integral component thereof.
Traditionally, refrigerated boxcars often have less inside height than desired for many types of lading and a relatively short interior length. Heat transfer rates for conventional insulated boxcars and refrigerated boxcars are often much greater than desired. Therefore, refrigeration systems associated with such boxcars must be relatively large to maintain desired temperatures while shipping perishable lading.
A wide variety of composite materials have been used to form railway cars and particular boxcars. U.S. Pat. No. 6,092,472 entitled xe2x80x9cComposite Box Structure For A Railway Carxe2x80x9d and U.S. Pat. No. 6,138,580 entitled xe2x80x9cTemperature Controlled Composite Boxcarxe2x80x9d show some examples. One example of a composite roof for a railway car is shown in U.S. Pat. No. 5,988,074 entitled xe2x80x9cComposite Roof for a Railway Carxe2x80x9d.
Ballistic resistant fabrics such as Bulitex scuff and wall liners have previously been used to form liners for highway truck trailers.
In accordance with teachings of the present invention, several disadvantages and problems associated with insulated boxcars, refrigerated boxcars and other types of temperature controlled railway cars have been substantially reduced or eliminated. One embodiment of the present invention includes a composite box structure with a temperature control system and an airflow management system satisfactory for use with a refrigerated boxcar or a temperature controlled railway car. Another embodiment of the present invention includes a composite box structure which may be satisfactory for use with an insulated boxcar. A composite box structure formed in accordance with teachings of the present invention combines benefits conventional railway car components with benefits of advanced plastic and composite materials. For one application a temperature controlled railway car may be formed in accordance with teachings with the present invention with enlarged interior dimensions of approximately seventy two feet, two inches inside length, nine feet, two inches inside width and an inside height at the center line of twelve feet, one and one half inches.
A composite box structure formed in accordance with teachings of the present invention provides enhanced insulation, increased load carrying capacity, better temperature regulation, increased service life, and reduced maintenance costs as compared to a typical refrigerated boxcar. The present invention allows designing side wall assemblies and end wall assemblies with insulating materials having optimum thickness to substantially minimize heat transfer rates between the interior and the exterior of a resulting composite box structure and to maximize interior load carrying capacity. Structural integrity of a resulting composite box structure may be maintained using conventional materials such as steel alloys to form exterior portions and supporting structures of the side wall assemblies and end wall assemblies.
A composite box structure for a railway car may be formed in accordance with teachings of the present invention with similar or reduced costs as compared to conventional refrigerated boxcars and insulated boxcars and with substantially improved load carrying capacity and thermal energy characteristics. Many structural members of the resulting railway car may be formed from steel alloys and other materials which may be easily repaired as compared with some composite materials. Composite materials with substantially improved insulation characteristics are used as nonstructural members to improve heat transfer characteristics while at the same time increasing load carrying capability.
A further aspect of the present invention includes a method of forming side walls and end walls for a composite box structure defined in part by a plurality of side stakes or support posts with metal side sheets attached to one side of the side stakes and at least one layer of ballistic resistant fabric attached to the opposite side of the side stakes with void spaces formed therebetween. The end wall assemblies and the side wall assemblies may be placed in a foam press with the respective assemblies tilted at an angle of approximately ten (10) degrees. Polyurethane foam or other types of insulating foam having high thermal insulation characteristics may be injected into void spaces formed between the side stakes, the exterior metal sheets and the interior ballistic resistant fabric.
Technical benefits of the present invention include covering the interior surface of metal components used to form the composite box structure with one or more layers of insulating material. For some applications strips of pultruded glass fiber trim may be placed on metal door posts and other metal portions of associated door frames. Blocks of polyurethane foam may also be installed at corner joints between associated side wall assemblies and end wall assemblies.
Forming side wall assemblies and end wall assemblies with all or at least portions of respective side sill assemblies and end sill assemblies as an integral part thereof allows optimizing associated fabrication techniques and reduces both cost and time required to complete manufacture and assembly of the resulting temperature controlled railway car or insulated boxcar. Various benefits associated with fabricating side wall assemblies and end wall assemblies in accordance with teachings of the present invention will be discussed throughout this patent application.